Two-time Indianapolis 500 winner and former Izod IndyCar Series champion Dan Wheldon died on Sunday in a horrific accident at Las Vegas Motor Speedway.

Wheldon, 33, was trailing a pack of cars when Wade Cunningham slowed after contact with fellow rookie James Hinchcliffe.

Several cars spun, and Wheldon, driving on the track's bottom groove, ran over the top of another car.

Pippa Mann, J. R. Hildebrand and Will Power also were taken to University Medical Center in Las Vegas for observation.

Wheldon won the Indianapolis 500 this year and in 2005. He was the IndyCar champion that year.

Wheldon started Sunday's race, the IndyCar season finale, at the back of the pack. He was competing for a $5 million bonus offered by IndyCar to any driver who was not a series regular who could win the race after starting last.

Despite winning this year's Indy 500, Wheldon had not been able to find a steady ride for the full IndyCar season. Earlier this weekend, Wheldon told Autoweek that he was close to signing a deal with Andretti Autosport, with which he won the Indy 500 in 2005, for a full-season ride in 2012, taking over the car being vacated by Danica Patrick, who is moving to NASCAR.

Wheldon is survived by his wife, Susie, and two young sons, Sebastian and Oliver.

IndyCar CEO Randy Bernard said in a statement: "IndyCar is sad to announce that Dan Wheldon passed away from unsurvivable injuries. Our thoughts and prayers are with Dan and his family."

After a two-hour delay, the race was canceled following a five-lap salute to Wheldon by the drivers.

In 1999, CART's season-ending race at Auto Club Speedway in Fontana, Calif., saw Greg Moore killed in an early-race crash in turn two.